From DE 39 29 294 A1, it is known to provide a mirror on such a light waveguide at one end and to couple light into it at the other end.
The light coupled into the light waveguide travels through it to the mirrored end, is reflected and travels back in the opposite direction through the light waveguide as a result.
The intensity of the reflected light is measured. If such a light waveguide is subjected to an ionizing radiation, the light damping in the waveguide is thus altered and so is the light intensity. The intensity change is a measurement of the radiation dose.
Light waveguides which, because of their composition, enable a tissue equivalent measurement of the radiation dose have a relatively low detection sensitivity.
The detection sensitivity can be increased by the use of long radiation-sensitive light waveguides. However, that increased detection sensitivity is connected with a correspondingly smaller local resolution.
In order to be able to measure approximate tissue equivalents with satisfactory local resolution and detection efficiency, according to German Patent application DE 195 03 647A1, two differently radiation-sensitive light waveguides are used.
However, the use of two waveguides, because of the large spatial requirements by comparison to a single waveguide also is detrimental with respect to the local resolution. Even here, proportionally longer light waveguides must be used with correspondingly poorer local resolution.